Lockable knee implants and related methods

ABSTRACT

Total knee replacements for hinged knee implants include a tibial member, a femoral member, a hinge assembly having a laterally extending axle configured to hingedly attach the femoral member to the tibial member, and a lock mechanism in communication with the hinge assembly. The lock mechanism is configured to (i) lock the femoral member in alignment with the tibial member for a full extension or other defined stabile walking configuration to thereby allow an arthrodesis or stiff knee gait and (ii) unlock to allow the femoral and tibial members to pivot relative to each other for flexion or bending when not ambulating.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/944,161, filed Jul. 17, 2013, which claims the benefit ofand priority to U.S. Provisional Application Ser. No. 61/672,352, filedJul. 17, 2012, the contents of which are hereby incorporated byreference as if recited in full herein.

FIELD OF THE INVENTION

The present invention relates to surgical implants and is particularlysuitable for knee implants used in the presence of muscular deficiencyor as an alternative treatment to knee arthrodesis.

BACKGROUND

Knee arthrodesis, indicated in the presence of inadequate muscularcontrol or soft tissue stability, allows for patients to successfullyambulate. This surgery results in a rigidly extended lower limb thatcannot be flexed or reduced in length. The extended position requiresgreater muscular strength and endurance to control, even when notmobile, which can lead to secondary joint pain and muscular fatigue. Thepermanence of this rigid extension can also prevent patientparticipation in many normal daily living activities such as bathing,tying shoes, or sitting in close quarter spaces such as a cars,airplanes and theaters.

Total knee replacement (TKR) is a surgical procedure to relieve pain,correct deformity, and restore knee function using artificial materialsto restore the load bearing and movement functions of the knee. Ifprimary treatment fails, a revision procedure is required. As the numberof knee replacement procedures increases, so does the incidence ofrevision surgeries. With each surgery more native anatomy is lost andthe risk of secondary damage to musculature, nerves and bone increases.Multiple surgical interventions can compound these risks and negativecomplications, and can lead to terminal knee dysfunction.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention provide lockable knee implants thatallow for knee flexion when desired by the patient, and that lock into afixed or semi-rigid configuration for structurally stable stance orwalking, similar to an arthrodesis or stiff knee gait.

The lockable knee implants can be selectively locked and/or unlocked bya user.

The lockable knee implants can have mechanical or electromechanicallocks to lock and unlock the knee implant, and thus the lower limb, intoa specific orientation for stance, walking, or the like, or to allow theknee to freely flex for sitting and the like.

The lockable knee implants can include a magnetically operated lock thatcooperates with an externally applied magnetic field to lock and unlockthe knee implant, allowing the knee to lock the lower limb into aspecific orientation for stance, walking or the like, or to allow theknee to freely flex for sitting and the like.

The lockable knee implants can be self-locking, responsive to applying adefined force or load, typically a load-bearing weight.

The lockable knee implants can include buttons, latches or flexiblesurfaces on the implant that are accessible by the user (throughpalpation or the like) either manually or with a tool, that can be usedto activate the locking or unlocking ability of the implant.

It is noted that aspects of the invention described with respect to oneembodiment, may be incorporated in a different embodiment although notspecifically described relative thereto. That is, all embodiments and/orfeatures of any embodiment can be combined in any way and/orcombination. Applicant reserves the right to change any originally filedclaim or file any new claim accordingly, including the right to be ableto amend any originally filed claim to depend from and/or incorporateany feature of any other claim although not originally claimed in thatmanner. These and other objects and/or aspects of the present inventionare explained in detail in the specification set forth below.

Other systems and/or methods according to embodiments of the inventionwill be or become apparent to one with skill in the art upon review ofthe following drawings and detailed description. It is intended that allsuch additional systems, methods, and/or devices be included within thisdescription, be within the scope of the present invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features of the present invention will be more readily understoodfrom the following detailed description of exemplary embodiments thereofwhen read in conjunction with the accompanying drawings.

FIG. 1 is an isometric perspective view of a knee implant according toembodiments of the present invention. The device is unlocked andpartially flexed.

FIG. 2 is an exploded view of the device shown in FIG. 1.

FIG. 3 is a side view of the device shown in FIG. 1. The device may belocked in this position.

FIG. 4 is a side view of the device shown in FIG. 1 in a partiallyflexed orientation. The device is unlocked.

FIG. 5 is a side view of the device shown in FIG. 1 and FIG. 3, withcomponents of the locking mechanism removed.

FIG. 6 is a side view of the device shown in FIG. 1 and FIG. 4 in apartially flexed orientation, with components of the locking mechanismremoved.

FIG. 7 is a sectioned midplane side view of the device shown in FIG. 1.The device may be locked or unlocked in this position.

FIG. 8 is a sectioned midplane side view of the device shown in FIG. 1in a partially flexed orientation. The device is unlocked.

FIG. 9 is an isometric view of the device shown in FIG. 1, andaligned/rotated about its flexion axis as shown in FIG. 3, FIG. 5, andFIG. 7. The device is in an unlocked state, and the femoral component isremoved for visibility.

FIG. 10 is an isometric view of the device shown in FIG. 1, andaligned/rotated about its flexion axis as shown in FIG. 3, FIG. 5, FIG.7, and FIG. 9. The device is in a locked state, and the femoralcomponent is removed for visibility.

FIG. 11 is a rear view of the device shown in FIG. 1, sectioned in afrontal plane across the center of the locking mechanism. The device isin an unlocked state.

FIG. 12 is a rear view of the device shown in FIG. 1, sectioned in afrontal plane across the center of the locking mechanism, as shown inFIG. 11. The device is in a locked state.

FIG. 13 is an isometric view of the device shown in FIG. 1, and rotatedabout its flexion axis as shown in FIG. 1, FIG. 2, FIG. 4, FIG. 6, andFIG. 8. The femoral component is removed for visibility. The device isunlocked.

FIG. 14 is an example of a knee implant system in position relative tothe femur “F” and tibia “T”.

FIG. 15 an example of an embodiment of the device with a mechanicalpushbutton for the locking mechanism according to embodiments of thepresent invention.

FIG. 16 is front view of the embodiment of the device seen in FIG. 15.

FIG. 17 is an embodiment of the device where the lock can occurvertically through the stem of the femoral and tibial componentsaccording to embodiments of the present invention, shown in the lockedposition.

FIG. 18 is a view of the embodiment shown in FIG. 17, in a flexed andunlocked position.

FIG. 19 is an embodiment of the device with another lock mechanism thatis configured with a latch that engages when the device moved into fullextension and/or a walking stable configuration according to yet otherembodiments of the present invention.

FIG. 20 is a side section view of the embodiment in FIG. 19.

FIG. 21 is a box diagram of exemplary actions of a method according toembodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now is described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Broken lines illustrate optional features oroperations unless specified otherwise. One or more features shown anddiscussed with respect to one embodiment may be included in anotherembodiment even if not explicitly described or shown with anotherembodiment.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. As used herein, phrases such as “between X and Y” and“between about X and Y” should be interpreted to include X and Y. Asused herein, phrases such as “between about X and Y” mean “between aboutX and about Y.” As used herein, phrases such as “from about X to Y” mean“from about X to about Y.”

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andrelevant art and should not be interpreted in an idealized or overlyformal sense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on”,“attached” to, “connected” to, “coupled” with, “contacting”, etc.,another element, it can be directly on, attached to, connected to,coupled with or contacting the other element or intervening elements mayalso be present. In contrast, when an element is referred to as being,for example, “directly on”, “directly attached” to, “directly connected”to, “directly coupled” with or “directly contacting” another element,there are no intervening elements present. It will also be appreciatedby those of skill in the art that references to a structure or featurethat is disposed “adjacent” another feature may have portions thatoverlap or underlie the adjacent feature.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus, the exemplary term “under” can encompass both anorientation of over and under. The device may be otherwise oriented(rotated 90. degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly. Similarly, theterms “upwardly”, “downwardly”, “vertical”, “horizontal” and the likeare used herein for the purpose of explanation only unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention. The sequence of operations (orsteps) is not limited to the order presented in the claims or figuresunless specifically indicated otherwise.

The term “about” means that the recited number or value can vary by+/−20%.

The term “sterile” means that the noted device or material meets orexceeds defined medical guidelines of cleanliness and is substantially(if not totally) without contaminants so as to be suitable for medicaluses.

Turning now to the figures, FIG. 1 illustrates an example of a totalknee replacement (TKR) implant 10 according to embodiments of thepresent invention.

As shown, the implant 10 includes a lower (tibial) member 20, an upper(femoral) member 30 with a locking mechanism 40 (also called a latch).The lower member 20 is attached to the tibia (“T”) and the upper member30 is attached to the femur (“F”) via respective stems 25, 35. The lowerand upper members 20, 30 can be connected via a hinge yoke 22. Thelocking mechanism 40 can be incorporated into the hinge that is attachedto the rotating platform area 121 using the hinge yoke 22.

The hinge yoke 22 can include a laterally extending channel or aperture122 ₂ that is aligned with channel 130 ₁ in the upper member 30 to holdan axle 50, typically inside an axle bearing 51, so as to allow theupper member 30 to pivot with respect to the lower member 20 via theaxle 50. The hinge yoke 22 can include a second channel or laterallyextending aperture 122 ₁ that holds a moveable locking member 52, shownas a pin or bolt, that can selectively slide to engage or disengage achannel 130 ₂ in the upper member 30 to (i) lock into a fullstabilization walking configuration (e.g., full extension) to allow anarthrodesis gait without requiring normal muscular strength and/orcontrol and (ii) unlock to allow the members 20, 30 to pivot relative toeach other for flexion or bending when not ambulating. FIG. 14illustrates an exemplary implant 10 in position relative to the femur“F” and the tibia “T”.

In some embodiments, the hinge yoke 22 can include first and secondspaced apart, laterally extending apertures or channels 122 ₁ 122 ₂(FIGS. 7, 9), one of which hold the axle 50 as discussed above and theother holding at least one slidable locking member 52. As shown, theaxle 50 may'be larger than the locking member(s) 52, but the reverseconfiguration may also be used. The axle 50 can reside behind thelocking member(s) 52 as shown. In other embodiments, the axle 50 residesin front of the locking member(s) 52.

In the embodiment shown, at least one slidable locking member 52includes two locking members, one on each side of the implant 10. Thelocking members 52 can slide inward and outward substantially inconcert, or be separately deployable.

The hinge yoke locking member(s) channel 122 ₁ can be configured as asingle channel with a constant diameter or with different diameters.Where more than one locking member 52 is used, the different lockingmembers 52 can have different sizes (e.g., diameters) and/orconfigurations or may have the same configurations and sizes. In theembodiment shown, the hinge yoke 22 includes a forward channel 122 ₁with a reduced diameter or inner extending lip 57 at a medial sectionthereof 57 (FIGS. 11, 12) or with two aligned laterally extending closedchannels (not shown), one for each of the two locking members 52 (wheretwo are used). Although shown as two locking members 52 a single lockingmember 52 or more than two may be used.

In some embodiments, the implant 10 can include a polymer insert 21forming part of the hinge/rotating platform as in conventional implants10. The locking mechanism 40 can be incorporated into conventional ornovel hinge/rotating platform systems.

In some embodiments, the insert 21 and/or hinge yoke 22 can be providedin multiple configurations that can be selected by a doctor for aparticular patient so that the doctor can choose one that locks thepatient's leg 5-10 degrees short of “Full extension” for a stablewalking configuration.

The implants 10 can be modular, interfacing with other implantablecomponents of a knee replacement system, allowing for adjustment of limblength and fixation angle. The implants 10 can be suitable for patientswho could undergo revision, but are at risk of complications that couldcompromise its success. The implants 10 can be used for patients withpoorly performing revision implants, but who do not desire permanentfusion (or amputation). The implants 10 can be used for patients thatotherwise would require fusion or amputation. The implants 10 can beused with patients having existing fusions who can “take-down” to thelockable knee implant to provide them with increased mobility or qualityof life. The implants 10 may also be used as a primary implant for afirst TKR surgery irrespective of whether a patient may have thecompromised tissue or bone structure as a precaution.

The implants 10 can have a hinge/rotating platform design and provideindustry standard stability. The locking configurations can beconfigured to fit modular revision TKRs. The interfacing configurationsof modular revision TKR implants can allow mix and match of componentsto custom fit to individual patients. The implant 10 can restore theknee joint function using a rotating hinge-like function with two axisof articulation, including articulating members 21, 30, which rotateabout axle 50, and articulating members 20 and 21, 22 which rotate aboutthe stem 23 (FIG. 7) of the hinge yoke 22, to allow the joint tofunction in a more normal fashion. In some embodiments, the implant 10can include a mobile, bearing-type sliding component that supports theyoke 22 and may allow for some Anterior/Posterior (AP) motion (notshown). For descriptions of conventional TKR designs, includingrotating, hinged designs, see, e.g., U.S. Pat. Nos. 5,358,527,5,800,552, 7,572,292, 7,753,960, 7,799,084, and US PUB 2010/0131070, thecontents of which are hereby incorporated by reference as if recited infull herein.

FIGS. 1 and 4 illustrate the implant 10 with the upper member 30partially pivoted relative to the lower member 20 allowing flexion. FIG.3 illustrates the implant 10 in a locked upright configuration forstable, weight-bearing walking.

The device 10 can be locked via mechanical or electromechanical lockingmechanism 40 that engages the hinge comprising the hinge yoke 22. Thelocking mechanism 40 is typically unpowered, but may be passivelypowered (e.g., inductively powered) without requiring an on board powersource. The lock can be selectively activated and/or deactivated by auser. The locking mechanism 40 can be manually or electronicallyactivated and/or deactivated.

A user can activate and/or deactivate the locking mechanism from onestate to the other. The device 10 can maintain its current status untilthe user intervenes.

The locking mechanism 40 may be self-activating in response to a largeload, such as a load bearing weight, being applied to the members 20,30, when the members 20, 30 are aligned in a substantially straight orother stable (walking) orientation (such that the pivot shaft of thefemoral and tibial components are substantially in-line so that the limbis substantially straight). This activation can be while a patient isprone on a bed or sofa by pushing against a foot board, for example, butis typically in response to standing upright. The activation can beinduced by a jolt, small jump or other movement to cause the mechanicallock to move to the lock orientation.

When members 22 and 30 are aligned as shown in FIG. 3, FIG. 5, FIG. 7,FIG. 9, FIG. 10, FIG. 11, and FIG. 12, each locking member 52 cantranslate axially within interior spaces 53, 54 of channels 122 ₁ and130 ₂ to lock and unlock the device 10. The lock is disengaged, as shownin FIGS. 9 and 11, when the locking members 52 reside entirely withinthe respective internal space 54 of channel 130 ₂ of member 30. The lockis engaged, as shown in FIGS. 10 and 12, when one or both lockingmembers 52 are in communication with the interior space 53 of channel122 ₁ of hinge yoke 22, blocking rotation of member 30 with respect tomember 22, and thus preventing flexion.

In some particular embodiments, an interruption 57 in the interiorchannel 122 ₁ that divides internal spaces 53 can take the form of areduced diameter, and can keep locking members 52 from physicallycontacting either other, or from traveling beyond a pre-determineddistance.

When the device 10 is rotated about axle 50, interference geometry 60 ofthe hinge yoke 22 blocks access of channel 122 ₁ and can serve to keeplocking members 52 from leaving interior space 54.

In some embodiments, as shown for example in FIG. 2, the lockingmechanism 40 can include a magnetic material 55, which can be a physical“permanent” magnet, that is embedded in, assembled, attached and/orconnected to the locking member 52. A cap 56 can be used to seal off themagnetic material 55 from bodily fluid. As shown in FIG. 2, the lockingmember 52 includes a receiving space that holds the magnetic material 55therein and cooperates with the cap 56 to seal the magnetic materialtherein.

With the use of an internal magnetic material 55, attractive orrepulsive axial (side-to-side relative to the implant body) force can beapplied to the bolts 52 with a user interface device 155 which can applyan external magnetic field (physical or electrical magnet via a userprobe, control or other user interface input device), causing thelocking member(s) 52 to translate laterally with respect to the implantbody 10.

In some embodiments, the polar axis of magnetic material 55 can bein-line with the axis of the lock, and external magnets in the samepolar axis can be passed over either side of the device 10, pulling thebolts medially and into an unlocked configuration as shown in FIG. 10and FIG. 12. By reversing the external magnets to the opposite polardirection, the user can pass the external magnets 155 m over either sideof the device 10 to move the locking members 52 medially to unlock thedevice 10 as shown in FIG. 9 and FIG. 11.

FIG. 14 illustrates that a tattoo or other externally visible marker 255can be applied to the skin of a patient over the locking mechanism 10 toprovide alignment information for directional reference for “lock” and“unlock” actions (which can be icons or other suitable visible indicia).

In some particular embodiments, the magnetic material 55 can be a rareearth magnet, which is typically much stronger than ferrous magnets.There are two conventional types of rare earth magnets, neodymiummagnets (e.g., neodymium-iron-boron) and samarium-cobalt magnets.

In some embodiments, the polar magnetic axis of magnetic material 55within locking members 52 can be aligned in such a way that the naturalstate of the implant is to remain locked until user intervention.

Magnetic material can be extremely brittle and can also be vulnerable tocorrosion (such as from the digestive acids in the body). The magneticmaterial can be sealed within the locking member 52 and cap 56. Themagnetic material 55 can be alternatively or additionally plated orcoated with a biocompatible material such as polyethylene to protectthem from breaking, chipping and/or for corrosion resistance. Particularexamples of rare earth magnets include Nd₂Fe₁₄B, SmCo₅ andSm(Co,Fe,Cu,Zr).

The magnetic material 55 can include a material that moves or changesviscosity in response to exposure to a magnetic field such as amagnetorheological fluid (also known as an MR fluid, available from LordCorporation, Erie, PA) or a ferrofluid. The fluids change viscosity whensubjected to a magnetic field.

The lock 40 can also or alternatively be a mechanical lock 58, as seenin FIG. 15, that can be manually pushed by a user to engage and/ordisengage the locking members 52. For example, a user can push againstskin on one side of the implant 10 to slide a pin in a defineddirection, e.g., inward or up or down, a distance sufficient todisengage a lock feature that engages or disengages the locking members52. FIGS. 15 and 16 illustrate an exemplary manually deployable pushbutton 58 that a user can use to engage or disengage the lockingmechanism 40, e.g., to slide locking members 52.

In some embodiments, the hinge yoke 22 can include a set of stacked domeor belleview washers, springs or other biasing members that can bias themovement in one direction (to the unlocked or locked position).

The locking mechanism 40 can be self-activating in response toapplication of load bearing weights as noted above.

The locking mechanism 40 can be a mechanical assembly that includes aset of stacked dome or belleview washers, springs or other biasingmembers that compress when a defined load is applied and allow a lockingmember to translate in a defined direction, e.g., sideways or up or downto engage a mechanical lock retention feature associated with the hingeyoke 22.

As shown in FIGS. 17 and 18, the locking mechanism 40 can be configuredso that locking can occur with a vertical lock member 52′, which residesin a channel 330 within the femoral component 30. When the user movesthe leg into full extension, locking member 52′ can slide down into analigned channel 230 of tibial component 20. When locking member 52′ isin simultaneous communication with both channels 230, 330 flexion cannotoccur and the device 10 is thus locked, allowing for ambulation. Whenthe user wishes to unlock the device, the user can lift the leg so thatthe tibial member is above the femoral member, and the locking member52′ will return entirely to the shaft 330 of femoral member 30, thusunlocking the device and allowing for flexion.

In some embodiments of the device 10, the locking mechanism 40 isconfigured so that locking can occur in response to when the device ismoved into full extension, as shown in FIG. 19 and FIG. 20. The lockingmechanism 40 can include an upwardly projecting member 45 that is incommunication with a spring or other resilient member 46 to bias themember in one position, e.g., the member 45 can be spring-loaded. Theupper femoral component 30 includes an interior wall 30 w. The upwardlyprojecting member 45 has a lip 47 or other shaped feature with ageometry shaped to interface with and secure with a defined depressionin the femoral component 30 interior wall 30 w. In this embodiment, thelocking mechanism 40 can be disengaged through the previously describedmethod of magnetics and/or a mechanical push button.

In other embodiments, the locking mechanism can be activated using aninductively powered circuit/switch based on an externally appliedinductive power source.

While the foregoing written description of the invention enables one ofordinary skill to make and use what is considered presently to be thebest mode thereof, those of ordinary skill will understand andappreciate the existence of variations, combinations, and equivalents ofthe specific embodiment, method, and examples herein. The inventionshould therefore not be limited by the above described embodiment,method, and examples, but by all embodiments and methods within thescope and spirit of the invention as claimed.

That which is claimed:
 1. A method of operating a total knee replacementimplant, comprising: bending a limb of a patient with a total kneereplacement implant having a tibial member attached to a tibia, afemoral member with a hinge having a laterally extending shaft hingedlyattached to the tibial member and a lock onboard the implant; andselectively actuating the lock by performing an action external to thepatient to lock the tibial member and the femoral member together in alocked walking configuration with a longitudinally extending axis of thetibial member in substantial alignment with a longitudinal axis of thefemoral member for structural stability.
 2. The method of claim 1,wherein the bending is carried out by selectively unlocking the lock inresponse to performing the action external to the patient; wherein theunlocked configuration allows increased bending of the knee relative tothe fixed walking configuration.
 3. The method of claim 2, wherein thetibial member has a bearing surface defined by a polymer insert thatholds the hinge, the method further comprising allowing the femoralmember to rotate relative to the tibial member.
 4. The method of claim1, wherein the selectively actuating is carried out by a patient withthe implant.
 5. The method of claim 1, wherein the lock comprises amagnet that slides, and wherein the selectively actuating is carried outby passing an external magnetic field over the lock of the implant inthe knee.
 6. The method of claim 1, wherein the selectively actuating ismanually carried out by physically pressing on an actuation member incommunication with the lock that resides under skin of a patient withthe implant.
 7. The method of claim 1, wherein the lock comprises atleast one magnet or magnetic material that slides in defined directionsin a channel offset from the laterally extending shaft to lock andunlock the implant in response to performing the action external to thepatient.
 8. The method of claim 1, wherein the shaft of the hinge isheld in a first channel extending through the tibial and femoral membersand the lock comprises first and second lock members that selectivelyslide in defined directions in response to performing the actionexternal to the patient to respectively lock and unlock the femoral andtibial members.
 9. The method of claim 1, wherein in the fixed walkingconfiguration the femoral member is locked in substantial alignment withthe tibial member to thereby allow at least one of arthrodesis or stiffknee gait.
 10. The method of claim 9, wherein the bending allowsincreased bending of the total knee replacement implant relative to thefixed walking configuration and allows the femoral and tibial members topivot relative to each other during non-ambulation.
 11. A method ofoperating a total knee replacement implant, comprising: performing anaction external to a patient to actuate an internal lock that is incommunication with a tibial member and a femoral member of the totalknee replacement implant of the patient wherein when unlocked theimplant allows flexion of a tibial member and a femoral member and, andwherein when locked the tibial member and the femoral member are lockedtogether for structural stability.
 12. The method of claim 11, whereinthe tibial member is hingeably attached to the femoral member with ahinge having a laterally extending shaft, wherein the internal lockengages the hinge, and wherein the hinge is an internal component thatresides under skin of the patient's body.
 13. The method of claim 11,wherein, in the locked configuration, the femoral member is locked intosubstantial alignment with the tibial member in a walking configurationto thereby allow at least one of arthrodesis or stiff knee gait.
 14. Themethod of claim 11, wherein, in the unlocked configuration, the flexionis carried out to allow the femoral and tibial members to pivot relativeto each other during non-ambulation.
 15. The method of claim 11, whereinthe internal lock comprises a magnetic member that is laterally slidablebetween defined directions in response to performing the action for theselective actuation of the internal lock between the locked and unlockedconfigurations.
 16. A method of controlling a total knee replacementimplant of a patient which comprises a femoral member and a tibialmember and an internal lock, performing an action external to thepatient to selectively lock and unlock the total knee replacementimplant, wherein, when unlocked, the femoral member and the tibialmember can pivot relative to each other for flexion duringnon-ambulation, and wherein, when locked, the femoral member and thetibial member are locked together for structural stability duringambulation and are more aligned relative to when unlocked.
 17. Themethod of claim 16, wherein the tibial member is hingeably attached tothe femoral member with a hinge having a laterally extending shaft,wherein the internal lock engages the hinge, and wherein the hinge is aninternal component that resides under skin of a patient's body betweenstems of the femoral and tibial members of the total knee replacementimplant.
 18. The method of claim 16, wherein the internal lock comprisesa magnetic member that is laterally slidable between defined directionsin response to the performing the action external to the patient.